1. Field of the Invention
The present invention relates to a luminescent device that emits light by converting electric energy to light. The luminescent device of the invention can, in particular, be suitably used as an organic electroluminescent (EL) device.
2. Description of the Related Art
Organic electroluminescent (EL) devices are attracting attention as promising display devices because they provide luminescence with high brightness at a low voltage. An organic electroluminescent device capable of emitting light with high brightness has been disclosed (for example, in Japanese Patent Application Laid-Open (JP-A) No. 2002-324679), which is produced by a wet method using a luminescent dopant having a relatively larger solubility in a solvent, because a dry method (vapor-deposition method) for the production of a thin film lamination is inferior in improvement of production efficiency due to the complexity of the production process. Further, organic electroluminescent devices that are even more improved in terms of luminescent brightness and durability are demanded.
In order to produce an organic electroluminescent device having an organic layer having a multilayer structure, it is necessary when forming a luminescent layer by the wet method that a solvent is selected that can dissolve a dopant at a sufficient concentration without also dissolving a lower layer that has already been formed. Further, when forming a luminescent layer by the wet method, such problems exist as nonuniformity occurring in a layer due to evaporation of the solvent in a drying step after coating, and there is difficulty in maintaining a constant layer thickness. There are also cases where impurities, oxygen and water contained in the solvent, the binder or the like adversely affect the luminescent layer to cause deterioration both of luminescent brightness and of the durability of the luminescent device.